I. Field of the Invention
The present invention relates generally to the fields of echogenic biomedical devices. More particularly, it provides a brachytherapy device and method of manufacturing echogenic biomedical devices.
II. Description of Related Art
Ultrasonic imaging techniques have become increasingly prevalent in medical diagnosis and therapy over the last decades. The field includes needle biopsy positioning and the identification of medical abnormalities and fetal status in utero. To create echogenicity in an object or device one must provide a difference between the acoustic impedance of the object and the acoustic impedance of the surrounding medium. In the medical field, the surrounding medium is biological tissue or fluids such as blood, cerebral spinal fluid, or urine.
In the field of brachytherapy where radioactive sources are inserted into an organ or diseased tissue the precise placement is critical for calculated dose therapy in the organ or diseased tissue to insure appropriate dosage to the diseased tissue. The location of numerous radioactive sites must be carefully controlled to obtain the necessary radioactive dosing throughout the tumor or disease site. In brachytherapy of the prostate gland, source placement can be determined by ultrasonic imaging of the implant needles located within the gland. The procedure under a sterile field is simple, rapid, and effective provided the gland is implanted with sources in a predetermined array. Following implantation the proper placement must be determined by x-ray or magnetic resonance imaging since current brachytherapy sources are minimally echogenic if at all. If voids are identified a second procedure may be required or additional time may be required to reposition the patient. The field would be greatly improved if the brachytherapy sources were echogenic so as to provide real-time imaging of proper placement of the actual source during the procedure.
For almost two decades a plethora of approaches have been developed to enhance the echogenicity of medical devices by modifying the surface of the device. In U.S. Pat. No. 4,401,124 issued to Guess et al., the reflection coefficient of a biopsy needle is enhanced by means of a diffraction grating composed of groves diagonally machined into the needle tip. Elkins in U.S. Pat. No. 4,869,259 echogenically enhanced the needle by particle blasting with 50-micron particles to produce a uniformly roughened surface. In U.S. Pat. No. 4,977,897, Hurwitz machined sounding apertures into needles to match the incident beam wavelength this improving sonographic visibility. Bosley et al. (U.S. Pat. Nos. 5,081,997, 5,201,314 and 5,289,831) modified catheters and other devices by incorporating glass spheres or high-density metal particles in the range of 0.5 to 100 microns or partially spherical indentations. Rammler (U.S. Pat. No. 5,327,891) used microbubbles containing medium contained in vanes and/or tracks to echogenically enhance catheters. Davis et al. varied the configuration of the stylet inside the biopsy needle creating a series of annular groves about the stylet to enhance echogenicity of biopsy needles (U.S. Pat. Nos. 5,490,521, 5,820,554, and 6,018,676). In U.S. Pat. No. 5,759,154 Hoyns utilized a masking technique to produce depressions comprising alternating rows of squares and diamonds on the surface around the circumference of the device. Terwilliger modified the stylet by creating concave surfaces on the distal tip end in U.S. Pat. No. 5,766,135 and in U.S. Pat. No. 5,769,795 included a hole in the distal tip end to form a concave surface to reflect the ultrasonic beam. Each of U.S. Pat. Nos. 3,351,049, 6,099,458, 6,074,337, 4,994,013, 6,080,099, 4,702,228, 5,163,896, 6,132,677, 6,007,475, 5,976,067, 6,030,333, 6,059,714, 5,713,828, 6,132,359, 5,342,283, 6,099,457, 6,010,445, 6,059,714, 6,060,036, 6,146,322, and 6,159,142 disclosure devices with smooth surfaces that are not reflective from all angles. These smooth surfaces, like the smooth surface of a non-treated needle, create a surface that must be perfectly perpendicular to the ultrasonic emitter/receiver to result in an echogenic pattern.
Sarkis et al. in U.S. Pat. No. 5,921,933 claims echogenic enhancement by impregnating the echogenic portion with ultrasonically reflective particles. Violante et al. in U.S. Pat No. 6,106,473 claimed an ultrasonically visible solid device in which the echogenic coating was applied to a solid matrix where the surface coating comprised bubbles of a non-gas material that changed phase to gas when heated.
However, each of these advancements in the filed of echogenic imaging contains limitations. In many, external modification of the surface is needed. This adds an additional and often expensive step to the manufacturing process. In other methods, the device modifications are such that the orientation of the device must be perfectly aligned with the ultrasonic emitter/receiver in order to be visible using echogenic imaging.
Another disadvantage of the current methods is the lack of means to consistently position implants without the use of additional processing. Current technology often requires the use of a several step process for placing radioactive sources into a tissue site including an imaging step after initial placement to determine where the radioactive sources were actually delivered in the tissue.
It would therefore be advantageous to have a device with enhanced echogenic properties without the need for an extra step in the formation of the device, the need for exacting positioning relative to the ultrasonic emitter/receiver during use, or the need for a separate imaging step during placement of radioactive sources.
This invention relates to echogenic biomedical devices and methods of preparing them. More particularly, to brachytherapy sources where it is imperative to determine the exact placement of the device within the body at the time of treatment and the placement is not easily visualized. One or all of the following techniques can monitor the post implant position: ultrasonic, radiographic, and/or nuclear magnetic resonance imaging. The device can be used to determine the exact location of tissue for surgical extraction using technology available to the radiologist for placement and the surgeon in the operating room for precise location immediately before the operation and conformation immediately after extraction in the operating room.
An embodiment of the present invention is a medical device having improved echogenic properties comprising a parabolic surface incorporated into the device. The parabolic surface defines a gas-filled body chamber. A radioisotopic component such as 26Al, 198Au, 115Cd, 137Cs 125I, 192Ir, 40K, 32P, 103Pd, 86Rb, 123Sn, 89Sr, 90Sr, 125Te 90Y, 91Y, 169Yb or a combination thereof may be inside the body chamber. Preferably, the radioisotopic components is 125I or 103Pd.
It is an aspect of the invention that the device comprises at least one spacer element connected to the body chamber. The device may comprise a plurality of spacer elements such as at least one spacer element at the proximal and/or distal end of the device.
It is an aspect of the invention that the device comprises a plurality of parabolic surfaces, each of the parabolic surfaces defining a body chamber. In certain embodiments, the body chamber may be connected to a spacer element and the spacer element connected to at least a second body chamber. The spacer element or the body chamber may further comprise a contrast material such as silver, gold, or tungsten. The contrast material may be adapted for nuclear magnetic imaging or radiographic imaging.
It is an aspect of the invention that the device may comprise a docking guide operatively attached to the spacer element or to the body chamber wherein the docking guide is at the proximal end of the device. The docking guide is configured to accept a radioactive source or a spacer element and may comprise as flexible joint or a non-locking docking port.
The parabolic surface generally has a density of 0.5-1.5 g/ml, or more preferably 0.8-1.2 g/ml, or even more preferably 0.9 and 1.1 g/ml. The parabolic surface may be adapted to provide multiple angles of reflectance for an ultrasonic beam which is directed at the device.
The device may comprise one or more synthetic polymers such as a liquid crystal polymer (LCP), Teflon, carboxylic polymers, polyacetates, polyacrylics, polyacrylamides, polyamides, polyvinylbutyrals, polycarbonates, polyethylenes, polysilanes, polyureas, polyurethanes, polyethers, polyesters, polyoxides, polystyrenes, polysulfides, polysulfones, polysulfonides, polyvinylhalides, pyrrolidones, rubbers, and thermal-setting polymers. Similarly, the device may comprise a material selected from the group consisting of albumin, cellulose, cellulose derivatives, gelatin, and gut or one or more metals such as titanium.
The device may be adapted to monitor the positioning of the radioisotopic component in a patient.
It is an aspect of the invention that the body chamber defines one or more voids, bubbles or channels. It is preferred that a void is between 0.1 mm and 0.9 mm in length or more preferably about 0.5 mm in length. There may be between 1-100 or more preferably between 1-10 voids in a body chamber. It is preferred that the body chamber defines one void. It is preferred that when the body chamber defines one or more bubbles, the bubbles be between 0.001 and 0.1 mm in diameter, or more preferably about 0.01 mm in diameter. When the body chamber defines one or more channels, they may be between 0.001 and 0.1 mm in diameter or more preferably about 0.01 mm in diameter. The channels may spiral at approximately 45xc2x0 to the long axis.
The device may be adapted for insertion into a mammal such as a human, and may be adapted for use in brachytherapy.
Another embodiment of the present invention comprises a method of manufacturing an ultrasonically visible device. The method comprises (a) obtaining a liquid crystal polymer (LCP) tube comprising a proximal and a distal end; (b) obtaining a LCP spacer element; (c) placing the spacer element in the proximal end of the LCP tube; (d) sealing the proximal end of the LCP tube containing the spacer element; and (e) sealing distal end of LCP tube, forming a body chamber, wherein the inner surface of the body chamber is a parabolic surface. An optional step of: (f) shaping the body chamber by heating the body chamber to form hemispherical repeating units on the body chamber may also be added. It is preferred that the heating is ultrasonic heating. Step (f) may occur before steps (c), (d) or (e).
The spacer may comprise a contrast agent such as silver, gold or tungsten or more than one spacer elements.
Yet another embodiment of the present invention comprises a method of manufacturing an ultrasonically visible device, the method comprising: (a) obtaining a liquid crystal polymer (LCP) tube comprising a proximal and a distal end; (b) sealing proximal end of the LCP tube; (c) placing a radioisotopic component into the LCP tube; and (d) sealing distal end of LCP tube, forming a body chamber containing the radioisotopic component, wherein the surface of the body chamber is a parabolic surface. An additional step: (e) shaping the body chamber by heating the body chamber to form hemispherical repeating units on the body chamber, may also be included. A preferred form of heating the body chamber is ultrasonic heating. Step (e) may occur before steps (b), (c) or (d).
Another embodiment of the present invention comprises a method of monitoring the implant position in a patient comprising: (a) inserting a medical device into the patient wherein the device comprises a parabolic surface defining a body chamber and a radioisotope component incorporated into the device; (b) directing an ultrasonic beam at the implant position; (c) reflecting signal from the ultrasonic beam off of parabolic surface; (d) collecting reflected ultrasonic signal; and (e) determining the location of the device in the patient from the reflected ultrasonic signal. The method may further comprise surgically extracting tissue from the patient.
An aspect of the invention is that the medical device comprises a nuclear magnetic or radiographic contrast agent and/or a brachytherapy source. More than one of the devices may be inserted in the patient, and the device may be used for breast lesion localization. The location of the device may be determined before an operation or after extraction of tissue from the patient.